Greek cities were often built in the vicinity of a steep hill called an acropolis that served as a citadel and upon which the principal temples were located for safety. The Acropolis at Athens is the most celebrated example. Throughout Greece numerous temples were built. Many illustrated the most rudimentary temple type—a simple rectangular chamber called the naos, the side walls extending to the front to form terminations for an open entrance porch containing two columns. This loggia was sometimes repeated at the other end. The next stage was the forming of freestanding porticoes, then a continuing of columns, flanking sides and ends, the naos thus being completely surrounded by a colonnade. This type was termed peripteral and was exemplified in most of the important monuments of the great period. In dipteral temples the surrounding colonnade was doubled.
No public mass worship took place within the temples, the naos being designed primarily to house the statue of the deity. The structures of the culminating period are unique for the subtle proportionings and refinements of all the members, which are integrated into a superbly adjusted whole. To prevent an appearance of sagging, as in the temple platform (stylobate), or of concavity, as in the outlines of columns, subtly curved or slanting lines were substituted for straight or vertical ones and served as optical corrections. To insure the desired proportions and delicate relationships, a body of traditional formulas was accumulated, using mathematical and geometrical devices.